I highly recommend this site to those interested in the state of photovoltaics in the world, and to those unaware of the woeful state of photovoltaics in America.  For example, of the 50 most productive photovoltaic installations in the world, 24 are in Spain and 20 are in Germany.  Only 4 are in the United States.  Spain is generating a total of 205 megawatts in this top 50 category, whereas the U.S. is generating only 30.  In the 51 - 100 most productive category, Germany dominates with 28 plants.  The U.S. has only 1.  In the 101 - 150 range Germany and Spain together have 46.  Again the U.S. has only 1.  The recommended site contains a wealth of information and useful links, and is an excellent starting point for anyone interested in this very "green" technology.

A brief survey of wind power indicates that the U.S. is better positioned in this case, with the world's 3 largest wind farms in operation and more in the planning stage or under development.  Since wind blows during both daylight and darkness, wind power certainly has some pluses in its column.  On the other hand, wind turbines are mechanical devices with gears and generators, and photovoltaic panels are considerably more maintenance free.  The American southwest rivals Spain for sunlight, and there doesn't seem to be any reasonable explanation for our failure to date to more fully exploit this national resource (aside from national priorities badly in need of review and possible reordering).

Photovoltaics is not the only technology for generating electric power from solar energy.  A second method entails the use of the thermal energy in sunlight (and even in the ambient air), and is particularly well suited to parts of the American southwest.  A large plant in Gila Bend, AZ, is in the works to utilize solar heat.  (See "Solar Without Panels" for example.)

The good news is that there are several green sources of energy that have been barely tapped into at the present time.  And none of them add carbon dioxide to the planet's atmosphere.  Of great practical importance is the expectation that tapping into these green technologies will be hugely lucrative in the future, particularly as "scrubbing" requirements become increasingly stringent for fossil fuel burning power utilities.  See Earth, the Sequel for in depth discussions of investment opportunities.